Can MVC Custom Error pages retain Route Values? - c#-4.0

Question

The MVC project that I am currently working on uses Regions so that we can localise pages etc.
I have spotted a problem with our Error page. We have turned the custom error pages on in the web.config file. If we are on a page lets say : /IT/News/Index and we get an error, when it redirects it will go to /Error and there will be no routevalue attached to it.
Is there away to ensure that the langauge routevalue is retained by the Error page?
I have searched around and cannot find a solution at the moment and was wondering if anyone else could help or point me in the right direction?
Hope that this all makes sense. Any help is much appreciated.

Answer 1

If you're getting physically redirected to /Error then it's not because of the MVC HandleErrorAttribute. It's probably due to your Web.Config having system.web/customErrors defined for error handling. Using the HandleErrorAttribute causes it to inject a specific view instead of the view you would have normally returned but does not redirect you to a different action by default. The problem is when redirected because of customErrors, there is no inherant information available to tell you where they came from. But using HandleErrorAttribute DOES cause some info to be populated for you. Specifically it creates a HandleErrorInfo to use as a view model and passes that to the view you specify. For example, here's one that is reigstered in the /App_Start/FilterConfig.cs file.
public class FilterConfig
{
public static void RegisterFilters(GlobalFilterCollection filters)
{
filters.Add(new HandleErrorAttribute {View = "Error"});
}
}
When you redirect to an error View using the HandleErrorAttribute, certain information is populated for you. The HandleErrorInfo view model will contain the ControllerName of the original controller requested, and the ActionName of the original action. Also, the ViewData and the TempData from the original request will be copied into the ViewData and Temp data for the request to the Error view. With that information it should have what you need. Be aware that not all errors happen inside of an Action however, and exceptions that don't happen in an action will not be caught by the HandleErrorAttribute. So you'll still need to use something like customErrors (or system.webServer/httpErrors if you're doing it inside of IIS7+) to handle exceptions that occur elsewhere in your app.
Here's a link to the HandleErrorAttribute file on CodePlex in case you're wondering what it does. HandleErrorAttribute.cs

Answer 2

I'm not sure if this solution meets you requirements. You can override in your base controller OnException and then redirect to a specific page.
protected override void OnException(ExceptionContext filterContext)
{
string controller = filterContext.RouteData.Values["controller"].ToString();
string action = filterContext.RouteData.Values["action"].ToString();
//get other stuff from routing
//here you can do redirect or other stuff
//if handled exception
//filterContext.ExceptionHandled = true;
base.OnException(filterContext);
}

Answer 3

It depends how you're getting to the error pages, really. If you're using an ActionFilter-based method to catch exceptions, then you can get route values from the context that gets passed into the OnException method. If you're using a redirect from a catch block, then you can push the relevant information into TempData or pass it directly as a parameter, depending on how you're doing that redirect.

Answer 4

You can add a custom HandleErrorAttribute or use a base controller to be inherited by all your controllers. Either way, you need to get the RouteData object, like this
var routeData = filterContext.RouteData;
with that object, you can get all the route values accordingly to your needs. Check the object definition in MSDN site for more detail
Say you have the following route
routes.MapRoute(
"Language", // Route name
"{language}/{controller}/{action}/{id}", // URL with parameters
new { language = "en", controller = "Sites", action = "Index", id = UrlParameter.Optional } // Parameter default
Then routeData.Values.Keys will tell you the name of the parameter and routeData.Values.Values the value itself
Then, wherever you handle the exception, you can store the route data in a TempData variable, like this
TempData["RouteData"]
And after that, it will be available on your error page
#model System.Web.Mvc.HandleErrorInfo
#{
ViewBag.Title = "Error";
}
<h2>
Sorry, an error occurred while processing your request.
</h2>
#TempData["RouteData"];